1. Field of the Invention
The field of the present invention relates to the medical imaging system of the type with an X-ray emitting tube.
2. Description of Related Art
X-ray tubes used in the medical field are of a known conventional structure. They generally include, as illustrated in FIG. 1, an emissive cathode 1 and a rotating anode 2 which forms the target of the electrons emitted by the cathode 1 and which is the location for producing X-rays. This rotating anode 1 is mounted on the rotor of a motor 3. The cathode 1, the anode 2 and the motor 3 are positioned in a metal or glass envelope 4, in which a high vacuum is established.
It will be noted that such X-ray tubes—to which very high voltages (100-150 kV) are applied—have very low yield and are the source of significant heat releases. This is the reason why provision is generally made for having a dielectric coolant oil circulate between the envelope 4 and an external sheath 5. For this purpose, a pump P is usually associated with the X-ray tube. This pump P will cause the oil to circulate between the envelope 4 and the sheath 5, and will send it back into a heat exchanger E for example with plates and cooling by circulation of water or with fins and cooling by air.
Generally, the possibility of strongly lightening the weight of the source of radiation and of reducing the volume is desired so as to allow faster displacements of the latter with more significant offsets if need be.
This is why it has already been proposed to move away the portion of the cooling circuit formed by the pump and the heat exchanger, for example into a maintenance room in the vicinity of the room in which the remainder of the imaging system is set up.
As this will be easily understood, this assumes the setting up of relatively long pipework in order to allow the fluid to circulate between this maintenance room and the X-ray tube. Lengths which may range up to 70 m or more are notably contemplated.
The materials of the pipes contemplated to this day for these applications are relatively permeable to moisture and loaded with water. Other sources of moisture exist, such as the expansion volume, the seal gaskets, the plastic materials, etc.
Now, in order to provide the sought-after electric insulation for the X-ray sources used in the field of medical imaging, the coolant oil should be very slightly loaded with moisture.
Medical imaging systems are already known from U.S. Pat. No. 6,286,998, which include dehydration systems used for dehydrating dielectric oil during the maintenance sequence outside the normal operation of the imaging system.
Such systems remain complex.
Moreover, further improvement of the quality of the dehydration of the dielectric oil is desired in order to attain better performance.